The invention relates to a hoist trolley assembly.
It is sometimes necessary to add to a hoist trolley assembly an auxiliary lifting apparatus with a faster lifting rate but a lower lifting capacity than that of the main lifting apparatus. One way of doing this is to place two lifting machines into the same hoist trolley. This is expensive and requires a special hoist trolley designed for two lifting machines. Alternatively, the auxiliary lifting apparatus may be placed in a separate hoist trolley with no drive equipment. This separate hoist trolley is then connected mechanically to the main hoist trolley. This solution is expensive and manufacturing-wise poor, because its implementation requires special parts designed exactly for this purpose. In addition, the order in which the main hoist trolley and the auxiliary hoist trolley without drive equipment are placed on their travel route affects the power supply implementation of the hoist trolleys that is difficult to alter.
The auxiliary lifting apparatus with a smaller lifting capacity may also be placed in a hoist trolley having its own drive equipment. A situation where the auxiliary hoist trolley carries a heavy load generates a problem in this arrangement. When the torques of the hoist trolley motors are of equal size, the friction of the main hoist trolley wheels is not necessarily enough, and they may start to slip. Slipping may damage both the wheel and the carrier of the wheel, which may be a rail, for instance. In addition any position measurement information is lost, if the position measurement sensor is connected to the slipping wheel.